Throttle body assemblies of this type can fulfill different functions in an internal combustion engine. In particular, throttle plate ports for regulating the amount of intake air must be mentioned here but also exhaust gas flaps, radiator bypasses, exhaust gas recycling valves, or intake manifold flaps can also be constructed in this manner. In this connection the demand for as tight as possible a closure of the bore through which fluid flows by the corresponding throttle plate is constantly growing in the field of modern internal combustion engines. In order to achieve a tight closure of this type it is a known practice, for example, to machine the housing and the plates very precisely or also to spray the throttle plate or the valve seat with sealants or to provide them with a sealing ring. However, this requires much time and effort in production and is thus associated with high costs.
Accordingly, EP 0 482 272 B1 discloses a throttle body assembly whose parts are injection-molded in sequence in the same mold, where in said throttle body assembly the plate is injected in the closed state, i.e. with its entire periphery abutting the outer housing. Thereby an optimized tightness is supposed to be achieved by the plate in the bore without additional components and without additional processing having to be carried out.
Furthermore, it is a practice known from DE 10 2005 023 613 B3 to produce a throttle plate port by injection-molding it with other parts of the throttle body assembly in sequence in the same mold in such a manner that the housing lying outside is made to be as rotationally symmetric as possible, whereby warping of the outer housing upon the action of heat is avoided. In this way a high degree of closure of the bore can also be achieved with injection of the throttle plate and the throttle plate shaft in the opened state.
However, these plates which are injection-molded with other parts in sequence in the same mold have the disadvantage that control of the amount of fluid, in particular in the case of small angles of displacement from the closed state, is possible only with difficulty since even with a small opening angle a relatively large free cross-sectional surface arises. Thus for other applications, in particular for throttle plate ports made of metal, different measures are known for improving the characteristic lines of the plates in this range. In particular, spherical zones at the housing are produced here. Producing spherical zones of this type is, however, not possible in the case of the known throttle plate ports which are injection-molded with other parts in sequence in the same mold due to the presence of undercuts and thus the impossibility of carrying out the ejection.